The present invention relates to mechanisms for chairs which adjust the pitch of the seat from front to rear. Often, different users of the same chair would like the chair to be pitched differently. Some might like the front lip of the chair to be higher and others might like it to be lower.
A number of cumbersome alternatives have been proposed in prior art patents for achieving these results, although it is not known whether any have been utilized commercially. U.S. Pat. No. 3,362,746 to Huyge issued Jan. 9, 1968 discloses a ratchet type mechanism for adjusting the pitch of a vehicle seat. The two U.S. Pat. Nos. to Costin, 4,054,318 issuing Oct. 18, 1977 and 3,954,245 issuing May 4, 1976, both disclose a cam type of arrangement for changing the elevation of the front of a seat. U.S. Pat. Nos. 2,221,268 to Sears issued Nov. 12, 1940, 2,638,150 to May issued May 12, 1953 and 2,646,839 to Hillman issued July 28, 1953 similarly disclose cam arrangements for changing the elevation of the front of a vehicle seat, and therefore for changing the pitch of the seat.
U.S. Pat. No. 4,076,308 to Slabon et al issued Feb. 28, 1978 introduces a seat pitch adjustment mechanism into a chair control. Chair controls normally function solely to control the rate of tilting of an office type chair. In the Slabon proposed mechanism, wedge blocks slide on ramps and are held in place by bolts. The bolts can be loosened with a tool so that the wedges can be slid to thereby change the pitch of the seat.
All of these mechanisms are cumbersome and tedious to operate. A noticeably greater force is required to adjust the pitch of the seats up than down. The Slabon mechanism is particularly tedious in that one has to first loosen bolts, slide wedges up or down a ramp, then make certain that both wedges are slid equally so that the pitch adjustment is the same on either side of the seat, and then retighten the bolts.